The first edition of the Dandy Comic cost just tuppence – and there was a free whistle on the cover, too. But 75 years on Desperate Dan, the title's best known character, has leered out of the lower shelves in the newsagents for the last time. On Tuesday the world's third-longest-running comic magazine will switch to online publication. Each new digital edition is expected to cost a little over a pound if bought singly – and there will be no free whistle.

Yet, according to DC Thomson & Co, the comic's Dundee-based publisher, Dan the cowboy has not eaten his last cow pie, and many of the other inhabitants of its pages, including Korky the Cat and Bananaman, will live on online.

Whether one of the great surviving symbols of a traditional British childhood can go on to thrive in a new medium will depend on the number of fans who take out subscriptions next week. The print title came out every week from its launch in 1937 until 1941, when paper shortages forced it to alternate weeks with sister title the Beano. By 1949 it had gone back to weekly editions and a year later it changed its name to simply the Dandy – the first in a series of infrequent efforts to modernise. With a circulation of 2m in 1950, the Dandy became the world's biggest-selling comic.

Now at the end of an "absolutely crazy" week preparing the secret contents of the new website, its 62-year-old archivist and former editor, Morris Heggie, said he believed the best was yet to come. "It is great fun," he told the Observer. "It is a long time since I have had sleepless nights over the Dandy, but this new site is classic Dandy and just fabulous. I think everybody will be surprised as to how it has been managed."

Heggie is enthusiastic, but admits his heart remains with the print edition: "I know all the reasons for the change, but I am a paper person.

"I grew up with a paper comic as a kid and then I edited it. I even loved the bad-quality paper after the war." Heggie said the look of the original pen-and-ink illustrations has never been bettered. "Nobody works in that style any more, although they try to replicate it on a tablet."

The archivist's grown-up children still make fun of him, he added, for reminiscing about the smell of a new DC Thomson Christmas annual. "There was this inky smell the first couple of times you opened it. It was a unique British style, too."

Initially, the comic's aim was to compete not with other comics, but with early American cinema cartoons such as Steamboat Willy, Heggie said.

Throughout 75 years of change the comic has reflected world events, and poked fun at itself as well. In 1941 Desperate Dan became a wartime hero, sinking U-boats and bringing down enemy planes with a peashooter. Hitler and Göring were ridiculed in a strip called Addie and Hermy, The Nasty Nazis, and Desperate Dan also punched Hitler all the way back to Germany.

"Dandy is a great survivor," said Heggie. "It even got through the graveyard shift that was the 1980s. Our long history helped us there, because it was being introduced to kids by mothers and dads and grannies who were quite happy with the content."

Desperate Dan was at the centre of a national outcry among fans in 1997, when he was temporarily "retired" following an edition in which he was shown sailing off into the sunset with the Spice Girls. DC Thomson later admitted this was a ruse to grab publicity for the comic's 60th anniversary. Four years later, Dan caused a stir again – when he gave up on his cow pies during the BSE outbreak.

Former editor Albert Barnes designed Dan as "the roughest, toughest cowboy. A man who can chew iron and spit rust" and Barnes' own face was said to have provided the inspiration for Dan's large and jutting chin.Over the decades the comic also provided a home for characters such as Beryl the Peril, Bananaman and Cuddles, who were adopted from defunct DC Thomson titles Nutty and Hoot.

A Dandy revamp in 2010 saw some of these old favourites elbowed aside to make room for new celebrity-based comic strips, featuring Harry Hill, Cheryl Cole, Simon Cowell, Jamie Oliver and Jeremy Clarkson. Sales continued to fall, though, and by the end of 2011 they were down 50%. At the beginning of this year DC Thomson decided to pull the Dandy, then priced at £1.99, from the industry circulation audit, and in the summer announced it would drop the print edition for good.

Fans of inky paper, such as Heggie, will be pleased to know there are still plans for a printed Dandy annual.

Next week, the much-loved comic the Dandy celebrates its 75th anniversary and will end the print version in favour of publishing online-only. Here we bring you some highlights of the eventful life of one of its most popular and enduring characters: Desperate Dan